Search found 1307 matches

by enricosavazzi
Mon Feb 08, 2010 6:20 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: Methods/equipment for precision focusing
Replies: 3
Views: 1563

Methods/equipment for precision focusing

In this post I try to summarise the methods/equipment that can be used for precision focusing in photomacrography with a current DSLR, from the obvious to the far-fetched, and their principal pluses and minuses. I am mainly covering the studio/laboratory techniques. Many of these techniques can be c...
by enricosavazzi
Mon Jan 18, 2010 2:02 pm
Forum: Equipment Discussions
Topic: Zeiss focus blocks
Replies: 5
Views: 2454

Actually, the best use is something like this, with camera/bellows vertical. I assumed from the earlier posts that this is the way you intend to use it. The scale of your montage should be approximately right. This is another Leica model I often use at present. The granite slab is a cheap patio/gard...
by enricosavazzi
Mon Jan 18, 2010 5:09 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: Left or right lighting?
Replies: 10
Views: 2307

It would not surprise me if editors would flip images (various categories of subjects, not just plants or animals) to get the required orientation (e.g. left view changed to right). I have seen it done for articles for general readership and have had my transparencies flipped. (The change which use...
by enricosavazzi
Sun Jan 17, 2010 1:05 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Left or right lighting?
Replies: 10
Views: 2307

... So are lateral views of insects meant to be looking left or right ? Andrew I am not an entomologist, so I don't know for sure if there are special conventions. For arthropods in general, when you have only dorsal and/or ventral views, they are most often vertical with the head uppermost. Latera...
by enricosavazzi
Sun Jan 17, 2010 12:25 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: Left or right lighting?
Replies: 10
Views: 2307

For illustrations of scientific literature, it is generally stated that the main illumination should come from a top-left direction. This is often specified as a requirement in the "instructions for authors" of scientific journals. It may be necessary to make exceptions, but in this case the directi...
by enricosavazzi
Sun Jan 17, 2010 4:09 am
Forum: Equipment Discussions
Topic: Zeiss focus blocks
Replies: 5
Views: 2454

This might also be something to consider: eBay item 270515876203. These are parts of Leica racks for stereomicroscopes. This particular one has only coarse focusing, but sometimes one finds models with both coarse and fine focus. The gear is steel/brass but the rack is plastic, which makes it potent...
by enricosavazzi
Thu Jan 14, 2010 7:18 am
Forum: Equipment Discussions
Topic: Zeiss Ikon Bellows
Replies: 4
Views: 1606

This type of bellows with fixed rear standard has a problem: when the bellows are closed at or near minimum extension, the front rails stick out and may be in the way of the subject, especially with a lens of short focal length. You might wish to check whether it is possible to mount the 4/3 camera ...
by enricosavazzi
Wed Jan 13, 2010 11:34 am
Forum: Equipment Discussions
Topic: Zeiss focus blocks
Replies: 5
Views: 2454

Well, the one at http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260535369591 seems to be the usual coarse/fine rack for the Universal and Photomicroscope models (from a U./P. II or III to be specific, but the rack from a P. I differs only for the paint colour). This rack has a coarse range of ap...
by enricosavazzi
Wed Jan 06, 2010 11:58 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: DOF and pupil ratio
Replies: 15
Views: 4283

... By the way, I measure my Luminar 16 mm f/2.5 as P=0.87 (exit pupil smaller). I wonder if the 25 mm is a different design, or is 1.1 using the other definition? ... --Rik They are somewhat different designs. The exit pupil of the 25 mm is visibly larger than the entry pupil. I believe the 16 mm ...
by enricosavazzi
Wed Jan 06, 2010 10:55 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: DOF and pupil ratio
Replies: 15
Views: 4283

At this point, I believe I can re-state one of the examples I mentioned in my original post. I now use the equations D = 2CE / (M^2/P^2), which I derived in one of the posts above, and E = N(M/P +1), which can be found in Lefkowitz or also easily derived. I define P = P_x/P_n, which seems to be more...
by enricosavazzi
Tue Jan 05, 2010 1:49 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: DOF and pupil ratio
Replies: 15
Views: 4283

rjlittlefield wrote: ...
Lefkowitz pg.258, effective aperture f_e versus marked f-number f_r: f_e = f_r*((m/P)+1)
...
Thanks, it figures out. Changing m to m/P wherever m occurs should in fact be enough to take P into account, but initially I got stumped over the unusual (1/P)+(1/m) part.
by enricosavazzi
Tue Jan 05, 2010 12:31 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: DOF and pupil ratio
Replies: 15
Views: 4283

mgoodm3 wrote:
It all works out to:

NA(working) = 1/(2*f-num*((1/P)+(1/m)))
Thanks. Do you have a reference for this equation?
by enricosavazzi
Mon Jan 04, 2010 5:14 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: DOF and pupil ratio
Replies: 15
Views: 4283

Enrico, The difficulty is that you have combined some formulas that incorporate P with other formulas that do not. An objective with m=20, NA=0.40, and P=1 is equivalent to an ordinary lens specified as f/1.19. The relevant formula in that case is that equivalent f-number is equal to 1/(2*NA)*(m/(m...
by enricosavazzi
Sun Jan 03, 2010 2:26 pm
Forum: Macro and Micro Technique and Technical Discussions
Topic: DOF and pupil ratio
Replies: 15
Views: 4283

When the math is all gotten correct (no easy task!), the result that you get by computing from NA directly is the same as the result that you get by carrying P all through the calculations. The DOF of an ELWD 20X NA 0.4 objective is the same as any other 20X NA 0.4 objective. --Rik Thanks for the c...
by enricosavazzi
Sun Jan 03, 2010 6:23 am
Forum: Macro and Micro Technique and Technical Discussions
Topic: DOF and pupil ratio
Replies: 15
Views: 4283

Re: DOF and pupil ratio

> Did you intend to write 2.9µm and 5.5µm for the DOF values of the Nikon M Plan objective? Yes, thank you for pointing out the mistake. Easy to miss a zero while converting from mm. I corrected the original post accordingly. > On the other hand, is it possible that the designated numerical aperture...